Famed British soprano Sarah Brightman has said she is postponing a planned 10-day trip to the International Space Station as a passenger aboard a Russian Soyuz spacecraft.

Roscosmos officials said the flight scheduled for September 1 would proceed without her, carrying cosmonaut Sergei Volkov and European astronaut Andreas Mogensen.

Brightman, 54, who paid more than $50 million for the opportunity to become the eighth "space tourist," cited "personal family reasons" for not proceeding with cosmonaut training and the flight, in a statement on her website.

While space flight can be gruelling, Eric Anderson, co-founder of Space Adventures, the Virginia company which brokered her trip, insisted she was still prepared to go at some future date.

"We've seen firsthand her dedication to every aspect of her spaceflight training, and to date, [she] has passed all of her training and medical tests," he said.